1. Field of the Invention
The present invention relates to an image forming device having a structure constituting the framework of a device main body, and a surface mobile body unit fixed to the structure and comprising a surface mobile body for supporting/transporting a toner image or a surface mobile body for transporting a recording medium. Further, the present invention relates to a unit position adjustment method of the surface mobile body unit relative to the main body of the image forming device.
2. Description of the Background Art
Conventional electro photographic image forming devices are widely used as copying machines, printers, plotters, fax machines and multifunction devices of the foregoing. In these image forming devices, a photosensitive body, as an image support, is electrically charged by a charging device, and is then exposed by means of an optical writing device or the like to form a latent image on the photosensitive body, this latent image being then developed with a developer agent in a developer device to yield a toner image. After being formed, the toner image is transferred to a sheet-like recording medium in a transfer device, and then the image transferred to the recording medium is fixed in a fixing device, to form thereby an image.
The main body of such image forming devices comprises a structure including steel-made front and rear side plates, a base member, stays and/or frames, and an outer cladding that covers the outer periphery of the structure. Inside the structure are housed, for instance, the photosensitive body, the charging device, the optical writing device, the transfer device, the fixing device, a paper feed device and the like.
When in such image forming devices parallelism cannot be maintained between a fixing roller in the fixing device and a paper transport roller for transporting the recording medium from the paper feed device, the transport directions of these rollers become offset relative to each other, which may give rise to problems such as paper skew and/or trapezoidal image.
Also, if the parallelism cannot be maintained between a rotating shaft of the photosensitive body and a rotating shaft of an intermediate transfer body of the transfer device (rotating shaft of a support roller in case of a belt-like intermediate transfer body), the distance between the photosensitive body and the intermediate transfer body varies along the axial direction, as a result of which the image transferred to the intermediate transfer body may exhibit density unevenness in the axial direction.
Similarly, if parallelism cannot be maintained between the rotating shaft of the intermediate transfer body and a rotating shaft of a paper transport roller, the movement direction of the recording medium in the portion in which the image is transferred to the recording medium and the movement direction of the intermediate transfer body may slant relative to each other, which can result in a slanted image being formed on the recording medium.
The above problems occur thus when parallelism cannot be maintained between surface mobile bodies for supporting/transporting a toner image, such as the photosensitive body, the intermediate transfer body and the like, and surface mobile bodies for transporting the recording medium, such as the paper transport roller, the fixing roller and the like. As a result, it becomes necessary to ensure high-precision parallelism between surface mobile bodies. Ways of improving parallelism between the surface mobile bodies include, for instance, enhancing component precision of the various components, and/or using special assembly jigs for high-precision assembly of the structure and the surface mobile body unit provided with the surface mobile bodies, during assembly of the image forming device.
However, enhancing component precision is both difficult and costly. Apart from inherent limits to component precision, the accumulation of component tolerances in image forming devices comprising a substantial number of components may result eventually in parallelism offset between surface mobile bodies. Ensuring parallelism between surface mobile bodies through enhanced component precision obviously requires reducing variability in the components themselves, but also reducing assembly error during assembly of the device. Assembly error reduction, however, is also subject to limitations.
On the other hand, using assembly jigs during assembly of the device requires a high-precision jig itself, which involves high-difficulty jig design and manufacture. Both the manufacture of the jig and the parallelism enhancement achieved through the use of such a jig are also subject to limitations.
There is thus a pressing need for image forming devices capable of ensuring parallelism between surface mobile bodies, with enhanced precision, in order to cope with ever more demanding high-quality imaging.
Technologies relating to the present invention are disclosed in, e.g.
Japanese Patent Application Laid-open No. 2004-13167,
Japanese Patent Application Laid-open No. 2002-296923,
Japanese Patent Application Laid-open No. 2000-242124,
Japanese Patent Application Laid-open No. 2000-109235,
Japanese Patent Application Laid-open No. S63-011922, and
Japanese Patent Application Laid-open No. H10-301432.